Preheat the oven to 375 degrees. Line a baking sheet with tin foil then place two (oven-safe) cooling racks on the baking sheet. This will help the chicken "air bake" which means the thighs cook evenly and will allow the chicken to be crispy on all sides.
Pour the buttermilk into a dish. In another dish, combine the panko, paprika, garlic powder, onion powder, sea salt, and freshly cracked pepper, to taste; mix until well combined.
Dip the chicken into the buttermilk then dip into the panko crumb mixture until evenly coated. Place the coated chicken onto the baking rack-lined baking sheet; repeat with the remaining chicken thighs.
Season the top of the crusted chicken thighs with a little more sea salt and freshly cracked pepper, to taste, then spray with cooking spray.
Place into the oven and bake for 25-30 minutes or until 170 degrees and the juices run clear. Remove from the oven and let the chicken rest for 5 minutes before serving. Enjoy.